Naphthenic acid compositions

ABSTRACT

PETROLEUM NAPHTHENIC ACID DISTILLATE IS STABILIZED AGAINST COLOR DEGRADTATION BY THE ADDITION OF SALICYL ANILIDE OR HYDROCARBYL PHOSPHITE.

3,652,663 NAPHTHENIC ACID COMPOSITIONS Carroll J. Wedel, Walnut Creek, and John D. Gardner,

Richmond, Calif., assignors to Chevron Research Company, San Francisco, Calif. No Drawing. Filed Mar. 5, 1969, Ser. No. 804,670 Int. Cl. C10g 41/00; C07c 61/00 US. Cl. 260-514 N 6 Claims ABSTRACT OF THE DISCLOSURE Petroleum naphthenic acid distillate is stabilized against color degradation by the addition of salicyl anilide or hydrocarbyl phosphite.

BACKGROUND OF THE INVENTION This invention relates to stabilized naphthenic acid compositions having improved color stability.

Naphthenic acids are generally recovered from petroleum. However, they may also be obtained from various other materials such as shale oil, coal tar or synthetic mixtures produced by oxidation of hydrocarbons.

The crude naphthenic acids are commonly derived from petroleum fractions in the form of alkaline sludges which are the product of washing the petroleum fractions with aqueous caustic solutions. The alkali metal naphthenates in the caustic extracts thus obtained are then usually acidified with mineral acids such as sulfuric acid or hydrochloric acid to release the crude naphthenic acid. Such crude naphthenic acids ordinarily are quite dark in color. Even those acids which are exceptionally light colored tend to turn quite dark during storage over a period of time.

It has been found that suitably light colored naphthenic acids can be produced from the crude acids by vacuum distillation to obtain a fraction free of impurities which apparently lead to color degradation. Also, it has been found that naphthenic acids may be contacted with formaldehyde or paraformaldehyde in the presence of sulfuric acid condensation catalyst to remove impurities in the form of a sludge which is separated by conventional means such as filtration, decantation and the like.

Naphthenic acids and derivatives have a great number of uses, practically all of which place a premium on the light color. For example, metal naphthenates such as cobalt naphthenates are commonly used for paint and varnishes where color quality is of the utmost importance. Copper and zinc naphthenates are also used in the treating of wood and mildew-proofing of fabrics which would be adversely affected by the off-color materials. In still other uses, such as the formation of emulsifying agents for insecticides, disinfectants, soluble oils and the like, the color is likewise important.

SUMMARY OF THE INVENTION It has now been found that stabilized naphthenic acid compositions are provided consisting essentially of a major proportion of petroleum naphthenic acid distillate and a minor proportion sufiicient to improve color stability of a member of the group consisting of salicyl anilide and hydrocarbyl phosphite having the structure:

wherein R is hydrogen or alkyl or aryl of not more than 8 carbon atoms provided that at least one R is not hydrogen.

United States Patent 3,652,663 Patented Mar. 28, 1972 DESCRIPTION OF THE PREFERRED EMBODIMENTS The salicyl anilide or phosphite in the stabilized naphthenic caid compositions of the invention may be employed in any proportion sufficient to improve the color stability of the petroleum naphthenic acid distillate. Amounts as small as 0.001% by weight are effective. Preferred ranges for optimum color stability and practical economics are from about 0.01 to about 2.0.

Suitable hydrocarbyl phosphites include those having alkyl or aryl substituents containing as much as 8 carbon atoms each in accordance with the above summary of the invention. Examples of such hydrocarbyl phosphites include trimethyl phosphite, diethyl hydrogen phosphite, butyl dihydrogen phosphite, hexyl dihydrogen phosphite, dioctyl hydrogen phosphite, trioctyl phosphite, phenyl dihydrogen phosphite, tolyl dihydrogen phosphite, triphenyl phosphite, phenyl dixylyl phosphite, etc. For present purposes, it has been found that diethyl hydrogen phosphite and triphenyl phosphite, as well as the salicyl anilide or mixtures thereof, are quite effective in the preferred compositions.

The compositions of the present invention are illustrated by a number of examples in the following table. These examples are in no manner intended to limit the invention as described.

In the examples, as shown by the table, the effect of the additives on color stability of naphthenic acid was determined under 300 F. heat test. In the heat test, g. of the naphthenic acid, with and without additive, starting at 100 F. was heated in a 400 ml. beaker with continuous stirring to 300 F. at a rate of 4 F. per minute and held at 300 F. for 14 minutes. The original and final colors of the naphthenic acid compositions were obtained using the accepted Gardner color method and Gardner color scale. On such scale, a color of 6 is about the color of lemon juice, whereas a color of 12 is about the color of apple vinegar.

In the examples of the table, the naphthenic acid was a highly refined naphthenic acid designed for the production of driers for paints and varnishes where color stability is critical. In the refining of the naphthenic acid, formaldehyde compounds had been used to remove impurities in the form of sludge separated from the acids. Unless otherwise specified, the original color was about 6 according to the Gardner scale.

For the purpose of the tests of the examples, the additives were combined with the refined naphthenic acid in appropriate amounts in accordance with the preferred practice of the present invention. However, the stabilized effect of additives is also obtained by their use in the re fining and other processing steps to which the naphthenic acids are subjected. For example, undesirable color changes which may occur during fractional distillation of the naphthenic acids are avoided by the addition of salicyl anilide or hydrocarbyl phosphite to the mixture to be distilled.

TABLE-Uoni1'niied Gardner color Ex. Weight No. Additive or treatment percent Orig. Fina 10+ 8.. Sallcly anilide 9+ 9... Methyl ethyl ketoxime 12+ 10.--- Epoxldized soybean oil 11+ 11 4,4'-meth ylene dianiline. 1 Diethyl hydrogen phosphi 9+ Triphenyl phosphite 9+ 14"... N2 Blowing during test 12+ 15. O2 Blowing during test--. 13+ 16. Filtrol 420 clay treat 10+ 17- Filtration (5 pore size) 10+ N,N-di-salieylldene propylene dla- 003 1a---- fi 11+ Butylated hydroxy toluene 0. 01 Distearyl thiodipropionate 0. 10 19 plus 10+ Topanol CA 0.10 Triphenyl phosphite 0. 20...- plus 7+ Salicyl anilide 0.05 Disltearyl thiodipropionate-- 0. 20

p us 21- Butylated hydroxy toluene 0. 8+

us Sallcyl anilide 0. 02

N0rE.-Plus and minus symbols indicate shades of darker or lighter colors, respectively, not sufficient to be rounded ofi to the next higher or lower number.

As seen by the foregoing test results, the hydrocarbyl phosphite, the salicyl anilide and the mixtures thereof were outstandingly effective in stabilizing the color of the petroleum naphthenic acid distillate. In the thermal tests, the compositions of the invention gave final Gardner colors of about 7, which were closed to the original 6+ Gardner color of the naphthenic acid compositions. By way of contrast, other widely accepted inhibitors as set out in the table resulted in unsatisfactory dark compositions.

While the character of this invention has been described in detail with numerous examples, this has been done by way of illustration only and without limitation of the invention. It will be apparent to those skilled in the art that modifications and variations of the illustrative examples may be made in the practice of the invention within the scope of the following claims.

We claim:

1. Stabilized naphthenic acid composition consisting essentially of a major proportion of petroleum naphthenic acid distillate and a minor proportion of at least 0.001% by weight sufiicient to improve color stability of a member of the group consisting of salicyl anilide and hydrocarbyl phosphite having the structure:

wherein R is hydrogen or alkyl or aryl of not more than 8 carbon atoms provided that at least one R is not hydrogen, or mixtures of said anilide and said phosphite.

2. The composition according to claim 1, wherein the color stability is improved by triphenyl phosphite.

3. The composition according to claim 1, wherein the color stability is improved by diethyl hydrogen phosphite.

4. The composition according to claim 1, wherein the color stability is improved by salicyl anilide.

5. The composition according to claim 1, wherein the color stability is improved by a /50 mixture of triphenyl phosphite and salicyl anilide.

6. The composition according to claim 1, wherein the color stability is improved by from about 0.01 to about 2.0% by weight of said anilide or said phosphite or mixtures thereof.

References Cited FOREIGN PATENTS 560,797 7/1958 Canada 2605l4 LORRAINE A. WEI NBERGER, Primary Examiner R. GERSTL, Assistant Examiner 

